This application claims the priority of German Patent Application No. 198 18 119.1, filed Apr. 23, 1998, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a process for manufacturing a covering, paneling, or trim part with a directly molded-on carrier. Furthermore, the present invention relates to a covering or trim part manufactured according to this process as well as to a casting mold therefor.
From German Patent Document DE-Al-24 44 267, a process is if known for manufacturing an object made of plastic on which at least one surface is covered with metal in an injection mold. According to this process, objects are manufactured which have fairly large surfaces whose appearance has to meet high demands, for example, refrigerators, bath tubs and certain automobile parts, particularly those used as an interior covering in passenger cars. In addition to a flawless surface, a corresponding high stiffness and resistance to warping are also demanded.
In the known process, an at least two-part injection mold is used. A metal sheet, which forms the decor part of the covering and trim part is placed in the injection mold and is premolded when the mold is closed. After the complete closing, the edge is clamped in between the two parts of the injection mold. This simultaneously results in a sealing of the mold toward the outside. When the injection molding compound is subsequently injected, it causes a further molding of the decor casting in the manner of a deep drawing operation. Simultaneously, connection with the injection molding material takes place. As soon as the injection molding material has hardened, the mold is opened and the covering and trim part is removed. It must then still be treated on its edge which is clamped during the injection molding. This aftertreatment requires high expenditures and is therefore expensive.
From German Patent Document DE 195 46 551 C1, a coated decor part is known. In this case, flat unformed sheet bars are placed in the injection mold and are formed by the pressure of the injected plastic material corresponding to the interior shape of the mold cavity so that they assume its shape. This document relates to the manufacturing of a covering and trim part in a so-called sandwich construction, i.e., with an upper and a lower covering as well as a plastic filling situated in-between.
Furthermore, a manufacturing process is known in which fiber-reinforced plastic materials are pressed behind the decors. These are pressing processes in which duroplastic (SMC) and thermoplastic (GMT) materials are used.
It is a disadvantage of the known pressing process that the material is deformed by a pressing operation, which means that the inserted decor part is placed in the mold in a “floating” manner. Furthermore, undercut contours are possible only to a very limited extent because the required mold parts must be moved together with the pressing movement in flowing material. Also, multiple molds cannot be used in most of these cases.
It is therefore an object of the present invention to a manufacture a covering and trim part that can be produced having an excellent surface and a high precision without any treatment after the molding injection. Furthermore, it is an object to produce a covering and trim part which is manufactured according to this process as well as a casting mold by means of which this process can be carried out.
In contrast to the known processes requiring the covering and trim part to be cut to its final size after removal from the injection mold, the cutting to size of the decor part takes place in the injection mold according to the present invention. This is an important advantage not only with respect to saving time, but also with respect to reducing cost. Reducing costs is important because, as a rule, such covering and trim parts are mass-produced articles. The molding injection is advantageously carried out at a temperature of approximately 150° C.
As a further development of the process for manufacturing the decor part, a layer of blind veneer is placed on a layer of fine-wood veneer and a layer of a nonwoven coating saturated with phenol melamine resin or only a layer of glue is arranged in-between. The layer of blind veneer is optional. The nonwoven coating stabilizes and seals the wood veneer so that, during the subsequent injection molding process, no injection molding compound can flow out onto the veneer front side. The adherence of the injection molding compound is achieved by a corresponding surface treatment of the last layer (nonwoven coating, bonding agent) or by the general surface roughness.
If no fine-wood appearance of the covering and trim part is demanded, but instead the visible surface is to be formed by metal or by metal provided with a coating, another embodiment of the present invention provides that a coupling layer, particularly a reactive hot-melt-type adhesive or a “dry” glue film, is applied to the backside of a sheet metal part, for producing the decor part. This layer is heated and/or activated by the injection molding compound. The basic principle of the process, specifically the cutting to size of the decor part during the closing of the injection mold and therefore inside the injection mold does not change.
The process according to the present invention for manufacturing decor parts with a decorative surface can be carried out by using, in addition to the above-mentioned materials, specifically real-wood veneer; metal, such as aluminum, steel or copper; and paper, textile or other fiber materials or fabrics.
In the process according to the present invention, the decor blank can be securely positioned in the injection mold. By means of a flow of plastic material against, particularly a central region of the decor component, sealing is automatically achieved between the decor back side and the carrier part. In addition, if the mold is equipped with a dipping edge extending around the outer contour of the part, a precise cut with respect to the contour of the decor part can be achieved during the closing of the mold. As a result, an excellent fit of the decor blank with respect to the mold contour and thus a good sealing is achieved.
It is also important that, by means of the injection molding process according to the present invention, complicated and undercut contours, as needed in the case of function elements, such as fastening hooks, locking devices for switches, and the like can be produced.
The process is also highly reproducible because the material for the molded-on carriers can be introduced in the mold in a reproducible manner. This is in contrast to placing a carrier into the mold during pressing of the decor blank, which necessarily results in tolerances in the case of the insertion weight and of the position of the inserted blanks.
The blank temperature required for the hardening of the reactive mass is preferably approximately 150° C. and is simultaneously used for the hardening, for example, of a duroplastic glue film. This permits a high degree of deforming of wood because, during the filling operation, a displacement of the veneer layers can take place with respect to one another.
The manufacturing of metal decor parts can take place in the same manner. In the case of metal decor parts, the plane or preformed sheet metal part, for example, made of aluminum or other metals, is either coated on the backside with a coupling layer (such as a reactive hot-melt-type adhesive) and is placed in the mold, or is placed in the injection mold together with a “dry” glue film and the injection takes place behind it. The thermal expansions, for example, of aluminum and resin/fiberglass compound are very similar so that a low-tension construction can be achieved in the case of this combination of materials.
When injecting behind wood veneers, paper and textiles, the required deforming can be achieved by a flowing-on of the injection molding mass. At relatively low degrees of deformation, this also applies to metallic decors, such as decorative metal sheets made of aluminum or other metals.
Finally, it is also advantageous that, by the use of a dyed material, the covering and trim part edges and the backside can be produced with a finished surface.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.